Analysis of the data of the Health Insurance Plan of New York Breast Cancer Screening Study indicates that in those patients whose cancers were found by screening the case fatality rate at all ages is almost half the case fatality rate of controls. Those data also indicate maximal benefit in young women resides in the detection of in situ cancers. Due to relatively low yield of these early lesions, CFR and projected 20-year survival is no different for all women screened from controls. We have shown that the yield of these early lesions can be maximized by aggressive screening and liberal use of biopsy. Twenty-year survival after a five-year screen can be raised 30 percent above HIP control level and as much as 70 percent above HIP screened level. Furthermore, where Bailar has indicated a net gain (or loss) from -4 to +8 lives/20,000 women using the HIP data, using his method and our data we find a savings of 25-27 lives/20,000 women by three year screening to date. These are lives that have been saved by mammography alone.